Synthesis and single crystal growth of SnS by the Bridgman‐Stockbarger technique

SnS is a promising candidate as PV absorber material according to the material properties and the Loferski diagram, but despite the numerous publications on this material, the intrinsic material properties are widely unknown and the theoretical possible values for efficiency are still far away from those achieved in reality. Due to the fact that this material is mostly grown as thin film material, bulk research is rare. The material synthesis and the melt growth of tin monosulfide (SnS) by using Bridgman‐Stockbarger technique have been investigated in this study. After first growth experiments produced polycrystalline SnS, a significant reduction of the growth velocity lead to samples with a high amount of single crystalline material. These samples were investigated in detail regarding the structural and optical properties by using XRD/HRXRD, chemical etching and photoluminescence.     

Nd:YVO4 crystal growth by Czochralski technique with a submerged plate

This paper is to investigate the growth of Nd:YVO₄ (yttrium vanadate) crystal by the modified Czochralski technique with a submerged plate. Numerical studies are performed to examine melt convection and heat transfer during Nd:YVO₄ growth. The attention is paid to study the effects of initial elevation of the submerged plate, crystal diameter, and melt level on melt inclusions. It is found that the increase in crystal rotation rate and crystal diameter, and the decrease in melt level will increase the axial temperature gradient at the edge and in the center of the crystal, and change the interface shape from convex to flat. The experiments are also carried out to confirm the feasibility of the proposed new technique for controlling melt inclusions in Nd:YVO₄ crystal growth.     

Evaporation induced diameter control in fiber crystal growth by micro‐pulling‐down technique: Bi4Ge3O12

Diameter self‐control was established in Bi₄Ge₃O₁₂ fiber crystal growth by micro‐pulling‐down technique. In accordance with Bi₂O₃‐GeO₂ phase diagram, the diameter was controlled due to compensation of solidification with evaporation of volatile Bi₂O₃ self‐flux charged into the crucible with excess. The crucibles had capillary channels of 310 or 650 μm in outer diameter. The crystals up to 400 mm long and 50‐300 μm in diameter were grown at pulling‐down rates of 0.04‐1.00 mm/min. The melt composition and the pulling rate were generally only two parameters determining solidification rate. As a result, crystals with uniform (± 10%) diameter and aspect ratio up to 10⁴ were produced without automation of the process. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth of SiGe bulk crystals with uniform composition by utilizing feedback control system of the crystal–melt interface position for precise control of the growth temperature

We developed an automatic feedback control system of the crystal–melt interface position to keep the temperature at the interface constant during growth, and demonstrate its successful application to grow Ge-rich SiGe bulk crystals with uniform composition. In this system, the position of the crystal–melt interface was automatically detected by analyzing the images captured using in situ monitoring system based on charge-coupled-devices camera, and the pulling rate of the crucible was corrected at every 1 min. The system was found to be effective to keep the crystal–melt interface position during growth even when the variation of the growth rate is quite large. Especially, the interface position was kept for 470 h during growth of Ge-rich SiGe bulk crystal when we started with a long growth melt of 80 mm. As a result, a 23 mm-long Si_0.22Ge_0.78 bulk crystal with uniform composition was obtained thanks to the constancy of the growth temperature during growth through the control of the interface position. Our technique opens a possibility to put multicomponent bulk crystal in a practical use.